extern void clockevents_set_mode(struct clock_event_device *dev,
enum clock_event_mode mode);
extern int clockevents_register_notifier(struct notifier_block *nb);
-extern void clockevents_unregister_notifier(struct notifier_block *nb);
extern int clockevents_program_event(struct clock_event_device *dev,
ktime_t expires, ktime_t now);